Magnesium base alloy



Patented Feb. 25, 1941 UNITED STATES MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Michigan No Drawing. Application December 26, 1939," Serial No. 311,003

3 Claims.

The invention relates to magnesium base alloys and more particularly concerns an alloy of this nature having a high degree oi? formability associated with other desirable physical properties, such as good tensile and yield strengths.

Magnesium alloys are being widely used in the structural arts where a light weight metal is highly desirable, such as for use in making castings, forgings, and the like. However, the use of these alloys in the rolled form to make sheet metal articles requiring forming operations, such as bending, drawing, and the like, has not progressed as rapidly due to the-.fact that, in general, alloys of good formability or ductility permitting relatively sharp bends to be made without the article developing external cracks, usually have inferior characteristics as regards their tensile and yield strengths.

It is, accordingly, the principal object of the invention to provide a magnesium base alloy which can be made into rolled sheet and the'like. possessing a sufllcient degree of ductility or formability at ordinary temperatures to be sharply bent, drawn or otherwise shaped, while having good tensile and yield strengths. Other objects and advantages will be apparent as the description of the invention proceeds.

My invention resides in the discovery that a magnesium base alloy composed of from about 0.05 to 0.3 per cent of barium, the balance being substantially all magnesium, is endowed with the afore-mentioned properties. The most desirable properties, as represented by excellent elongation associated with good tensile and yield strengths is observed in those alloys containing between about 0.15 to 0.25 per cent of barium.

The following table lists some of the properties of rolled sheet metal made from my new binary alloy, as well as the properties of rolled sheet made from magnesium and a magnesium-barium alloy of higher barium content than my new alloy. Examination of the table shows the improvement in ductility and yield strength of the new alloy over that of magnesium and also the improvement over a magnesium-barium alloy having a higher percentage of barium than my new alloy. In the table the percent elongation is to be regarded as a measure of the ductility or formability.

The properties listed in the above table under the term, annealed" were obtained by first rolling the specimens at a temperature of between 600 and 800 F. and thereafter annealing them at various temperatures in the temperature range from 400 to 800 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. By a comparison of the properties listed in the above table it will be observed that the ductility or formability as represented by the percent elongation of the new alloy, shows a marked increase over that of a specimen consisting entirely of magnesium. At the same time, it will be noted that the yield strength has not fallen ofi while the tensile strength is increased over that of magnesium. The table also shows, that only a, limited amount of barium can be employed as an alloying ingredient while maintaining the desired property of improved elongation. When the percentage of barium exceeds the limits set for the new alloy composition, the percent elongation falls ofi. rapidly until at 0.8 per cent of barium the elongation value is very poor.

While the new alloy is most useful in wrought form, such as sheets, due to its formability characteristics, it may also be used for making castings, extruded forms and the like.

The new alloy may be compounded in any of the ways known to the art, such as adding the barium to molten magnesium under suitable flux which should be preferably free from magnesium chloride. If magnesium chloride is present in the flux it is desirable to add the barium without too much stirring, for otherwise the barium will be lost into the flux.

I claim: Y

1. A magnesium base alloy containing 0.05 to 0.3 per cent of barium, the balance being magnesium.

2. A magnesium base alloy containing from 0.15 to 0.25 per cent of barium, the balance being substantially magnesium.

3. A magnesium base alloy containing 0.2 per cent of barium, the balance being magnesium.

JOHN C. MCDONALD. 

